1. Field of Invention
The present invention pertains to shifting tools used in subsurface well completions, and particularly to hydraulic shifting tools used in closed hydraulic volumes.
2. Related Art
Shifting tools are commonly used in well completions in which actuation of a tool is brought about by relative movement of a tool element. This can be, for example, opening or closing a valve (e.g., sleeve, ball, or flapper), setting a packer, or initiating an explosive train. The earliest shifting tools were simple mechanical devices that engaged a profile in the tool element to be moved, and the tool element was moved as an operator manipulated the shifting tool.
More sophisticated shifting tools use hydraulic pressure to apply a force to a moveable element, such as a piston, to induce motion of the element. Existing hydraulic shifting tools generally require a fluid path to the surface or well annulus to permit movement of relatively incompressible well fluids. If such tools are run into a sealed volume, the tool will be stopped from advancing, and the piston will be prevented from moving, unless the fluid within the volume is routed to the surface or well annulus.